Project Summary: Identifying Genetic Loci Associated with Neurocristopathies using the Deer Mouse, Peromyscus maniculatus The neural crest is a multipotent progenitor cell type that contributes to multiple tissues throughout the body, including the peripheral nervous system, craniofacial tissues, the heart, and melanocytes. People with mutations that affect neural crest development can develop neurocristopathies, a broad class of congenital diseases that are often associated with pigmentation defects. Therefore, the rationale for this proposal is that identifying causative mutations for pigmentation defects in deer mice, Peromyscus maniculatus, will increase our knowledge of genetic lesions that can disrupt neural crest development and cause neurocristopathies. The dominant spot mutation in P. maniculatus results in a white blaze on the forehead of heterozygotes and is embryonic lethal when homozygous. The overall objective of this proposal is to capitalize on the unique features of P. maniculatus as a model system to identify the causative mutation for dominant spot. Our preliminary data show that dominant spot is linked to a 1.7 Mb interval on chromosome 20, which contains the neural crest regulatory gene Sox10. Sequencing of Sox10 exons from dominant spot homozygous embryos did not identify any sequence variants co-segregating with the phenotype, suggesting that the mutation is in a Sox10 regulatory sequence. In addition, we have found that the size of the forehead blaze varies dependent on the genetic background, suggesting the presence of modifier genes. These data have led to our central hypothesis that dominant spot results from a mutation in a regulatory region of Sox10 and that modifier genes cause variability in the dominant spot phenotype by interacting with Sox10 gene expression. This hypothesis will be tested by pursuing two specific aims. First, we will use target enrichment and high throughput sequencing to identify sequence variants associated with dominant spot. Second, a quantitative trait loci (QTL) analysis will be used to identify QTLs that are associated with the variability in spot size. This proposal is innovative because we propose to develop P. maniculatus as a model system for studying neuroscristopathies. The results from the proposed research will be significant because identifying the causative mutation for dominant spot and its genetic modifiers will increase our understanding of the neural crest gene regulatory network and provide genetic loci of clinical significance for screening in human neuroscristopathies.